While in the Minkowski spacetime \(i^0\)  is a regular point of the
conformal structure, it is well known that for spacetimes with
non-vanishing (ADM) mass one has a singularity of the conformal
structure —see e.g. [1]}, Chapter 20. This fact makes the
analysis of the gravitational field particularly
challenging. To address this difficulty it is necessary to
introduce a different representation of spatial infinity which, in
turn, allows to suitably resolve the structure of the gravitational
field in this region. In particular, to avoid having to deal with
directional dependent limits at spatial infinity it is natural to blow
up the point \(i^0\)  to a 2-sphere.
